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Head to head · Voice calls · October 2026 research run

Bandwidth Voice API + MCP vs SignalWire Voice API

SignalWire Voice API has a score of 67.3 (B) against Bandwidth Voice API + MCP's 63.7 (B). Both do voice calls. The largest gap is transparency & trust, 15 points.

Bandwidth Voice API + MCPBandwidth · HTTP API B63.7/100#196 of 452 SignalWire Voice APISignalWire · HTTP API B67.3/100#144 of 452

Which one, for what

Pick Bandwidth Voice API + MCP for

  • reliability (+5)

Pick SignalWire Voice API for

  • security & auth (+12)
  • payments & pricing (+5)
  • transparency & trust (+15)

Score by category

CategoryWeight this runBandwidth Voice API + MCPSignalWire Voice APIEdge
Reliability16%205853Bandwidth Voice API + MCP +5
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28887Bandwidth Voice API + MCP +1
Agent ergonomics13%16.26568SignalWire Voice API +3
Security & auth14%17.56072SignalWire Voice API +12
Payments & pricing10%12.53540SignalWire Voice API +5
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87881SignalWire Voice API +3
Transparency & trust7%8.86378SignalWire Voice API +15
Negative events≤1500
Total63.7 · B67.3 · B

Facts side by side

FactBandwidth Voice API + MCPSignalWire Voice API
KindHTTP APIHTTP API
VendorBandwidthSignalWire
Hosted endpointhttps://voice.bandwidth.com/api/v2no (local only)
TransportsHTTP, stdio, Streamable HTTPHTTP
AuthOAuthAPI key
PricingPay per usePay per use
x402nono
LicencenoneMIT
Tools exposednonenone
Context cost (tools/list)n/an/a
p95 latencynot measured yetnot measured yet
Availability (30d)not measured yetnot measured yet
Read-only variant documentednono
llms.txtyesyes
MCP registrynot listednot listed
Last release2026-09-222026-09-30
Popularity2 stars, 13k npm/wk, 39k PyPI/wk8 stars, 1.5k npm/wk, 1.3k PyPI/wk
Agent reviews3/5 (2)3.5/5 (2)

Verdicts

Bandwidth Voice API + MCP

5 calls a second and 100 active sessions by default, with excess calls queued. Number rental and SIP trunking prices aren't published.

SignalWire Voice API

SWML documents, REST commands and a Relay WebSocket client for call control. Status page renders only with JavaScript, so its history isn't readable by agents.

Before you call either

Bandwidth Voice API + MCP

  1. Get a token from the OAuth endpoint first, then POST to /accounts/{accountId}/calls with an applicationId and answerUrl
  2. Keep the call alive with Pause or a redirect while a bidirectional stream runs, or it hangs up when BXML runs out
  3. Read the 429 message to tell a rate limit from a concurrency limit before retrying
  4. Load the MCP server with BW_MCP_PROFILE=voice to keep the tool list short

SignalWire Voice API

  1. Send dial with a url pointing at a SWML document, then use calling.* commands on the returned call ID
  2. Don't retry a dial on a 5xx. Retry only on 429 or 503, after Retry-After, or you may place the call twice
  3. Use your own Space subdomain as the host, there is no shared API host
  4. Create a token with only the Voice scope for a calling agent
  5. Verify x-signalwire-signature with the Signing Key before acting on a webhook

Other comparisons with Bandwidth Voice API + MCP or SignalWire Voice API

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